Di-electric Grease

Hi,

This is probably very elementary, but what is the pupose of di-electric grease?

Where do I use it on a new ignition wire set that I am installing?

Specifically, on the distributor side of the wire does it go on the metal contacts? (The boot part seems to be coated already.)

Thanks for any infomation.

Larry

"dielectric" refers to a material that does NOT conduct electricity. Dielectric grease is used on spark plug and distributor tower boots to prevent the boot sticking to the tower or spark plug without causing a risk of flashover (the spark current grounding out along the tower or plug insulator, which it could do if the grease *did* conduct electricity).

On the boots on both ends.

There's no need to do so, though there'll be no harm if some gets there.

DS

I was under the impression that the main purpose of the dielectric grease was to seal the boot to keep out moisture and grime that might cause a short.

Regards,

Ed White

Approximately 8/21/03 15:12, C. E. White uttered for posterity:

The dielectric grease fills the void, which does tend to help keep water, etc. out. Even better, since it is a dielectric, if any water gets close to the boot, the grease helps keep the high voltage from tracking along the water path and away from the plug. Helps prevent corrosion too.

Dielectric refers to materials in which the charged particles are bound strongly to constituent molecules, very slight conductivily - dielectric grease is a polarized dielectric that supports an electric field (I is a physicist). If you find one that does NOT conduct electricity (outside a perfect vacuum), you get a Nobel prize. But for the most part, you're absolutely right, they are very weak conductors (order of

1020 worse than a good conductor). I just give a blob in each boot on both ends of the wire. It's a field that you are trying to pass down the wire anyway

Andrew

Daniel J. Stern wrote:

Ahhh. My di-electric questions are at last answered.

I thought it was SUPPOSED to conduct electricity and protect contacts from corrosion (by means of direct application to the contacts).

If I'm getting it, I was partially right. It doesn't 'help' conduct the electrons as much as the field passing down the wire.

perzacaly - you've got it - keeps low resitance path from forming, keeps moisture out, allows HV field to pass -

Andrew

Clem wrote:

I'd say its about 50/50 between sealing out dirt and providing better insulation to prevent flashover. It does both.

Dielectric = insulator (I are a engineer) :-)

Yes, all th> Dielectric refers to materials in which the charged particles are bound

sorry about the font - the 1020 should read 10 to the twentieth - big number.

And Steve is exactly right.

Steve wrote:

It does NOT keep a low-resistance path from forming, unless you take great care to try to keep the grease unmolested between the two contact surfaces. The contacts scrape away the grease at the points of contact.

I would hope that a 40K+ voltage could arc across a thin dielectric layer, but what I meant is it keeps moisture from getting into the boots and causing some cool arc traces on the outside. Even if you can't get the contacts to wipe the grease away, it does not matter much (if at all) - sort of like when you were little walking across the carpet in your socks and pointing your finger at the light switch - air (dry) dielectric is something like 35K/inch - did you know you had it in you? The rise time of an auto spark means that you are dealing in fields, not DC currents.

Andrew

Clift>Andrew Paule wrote:

It might be fun to study the fields. Resistive wire, capacitive load, transmission-line effects, instantaneous current at flashover/breakdown... one could almost do a doctoral thesis on one plug firing. :)

Bet it's been done...

Mike

"Clift>